Continued support is sought for a multifacetd study of human and experimental muscle diseases with light, phase electron microscopy, electron microscopic cytochemistry, immunoelectron microscopy, tissue culture methods and correlative biochemical and electrophysiologic investigations. Ultrastructural reactions of the muscle fiber organelles and quantitated by morphometric methods. Myasthenia gravis and its experimental autoimmune model will be investigated by methods involving the ultrastructural localization of the acetylcholine receptor, antibody against the receptor, and components of the complement system. The interactions between acetylcholine receptor, antibody complement components, the pathogenesis of the destructive changes at the end-plate and the mechanisms of impaired neuromuscular transmission and recovery will be analyzed. In Duchenne dystrophy cultured muscle fibers will be examined for evidences of the plasma membrane abnormalities observed in vivo.